Oil accumulated within a subterranean oil-bearing formation is recovered or produced therefrom through wells, called production wells, drilled into the subterranean formation. A large amount of such oil may be left in the subterranean formations if produced only by primary depletion, i.e., where only formation energy is used to recover the oil. Where the initial formation energy is inadequate or has become depleted, supplemental operations, often referred to as secondary, tertiary, enhanced or post-primary recovery operations, may be employed. In some of these operations, a fluid is injected into the formation by pumping it through one or more injection wells drilled into the formation, oil is displaced within and is moved through the formation, and is produced from one or more production wells drilled into the formation. In a particular recovery operation of this sort, seawater, field water or field brine may be employed as the injection fluid and the operation is referred to as a waterflood. The injection water may be referred to as flooding liquid or flooding water as distinguished from the in situ formation, or connate water. Fluids injected later can be referred to as driving fluids. Although water is the most common, injection and drive fluids can include gaseous fluids such as air, steam, carbon dioxide, and the like.
Water may be injected by itself, or as a component of miscible or immiscible displacement fluids. Sea water (for offshore wells) and brine produced from the same or nearby formations (for onshore wells) may be most commonly used as the water source.
GB Patent Specification Number 1,520,877, filed Oct. 14, 1974, discloses that secondary recovery of oil from a permeable stratum is effected using as a drive fluid water whose ionic compositions and/or ionic concentration has been adjusted in a reverse osmosis desalination plant so that the water is compatible with the stratum and the connate water associated therewith. Seawater is treated by the reverse osmosis desalination plant to remove a major proportion of the divalent or higher valency ions and to have its ionic concentration adjusted either by mixing the filtrate and concentrate in predetermined proportions or by recycling the concentrate from each cycle at a higher feed pressure. Particles having a diameter of at least 1 micron may initially be removed by ultrafiltration apparatus.
U.S. Patent Application 2003/0230535 discloses a method and well for desalinating saline aquifer water, wherein saline aquifer water flows from a subsurface aquifer layer directly into a downhole aquifer inflow region of a desalinated water production well in which a downhole assembly of one or more desalination and/or purification membranes is arranged, which separate the saline aquifer water into a primary desalinated water stream which is produced through the well to surface and a secondary concentrated brine reject stream, which can be disposed into a subsurface brine disposal zone.
Referring to FIG. 1, there is illustrated prior art system 100. System 100 includes body of water 102, underground formation 104, underground formation 106, and underground formation 108. Production facility 110 may be provided at the surface of body of water 102. Well 112 traverses body of water 102 and formation 104, and has openings in formation 106. A portion of formation 106 may be fractured and/or perforated as shown at 114. Oil and gas may be produced from formation 106 through well 112, to production facility 110. Gas and liquid may be separated from each other, gas may be stored in gas storage 116 and liquid may be stored in liquid storage 118.
There is a need in the art for improved systems and methods for producing oil and/or gas from a subterranean formation. In particular, there is a need in the art for systems and methods for providing an improved water flood.